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I was reading an article in the February 2022 issue of Scientific American titled “The Origins of Space and Time” by Adam Becker.1 The article suggests that space and time, which we take to be fundamental properties of the universe, might in fact be emergent properties created by something deeper that we don’t quite understand.2
Becker examines recent attempts by physicists to reconcile the big world of general relativity, where space and time (or spacetime) are shaped by gravity—and where we humans happen to live—and the tiny world of quantum mechanics, where gravity seems to be nonexistent or have no apparent function. Physicists have long spoken of a theory of “quantum gravity” that would reconcile the two realms. In the article, Becker examines several such attempts.
One attempt that’s been around for a while is string theory, which is a purely mathematical conjecture, positing every subatomic particle as being a tiny loop of string that exists in several dimensions and vibrates continuously. Another attempt combines a special interpretation of the spacetime from general relativity called “anti–de Sitter space” (AdS) with a variation of quantum theory called “conformal field theory” (CFT) to explore how subatomic particles become entangled in a relationship that can exist over vast distances. The suggestion is that these entanglements might knit together the reality that we perceive as space and time. A third attempt cites a theory, again from quantum mechanics, called “loop quantum gravity” that views space and time as tiny, discrete bits that are bound by one- and two-dimensional connections that create a “spin foam,” and this spin foam creates for us the illusion of space and time being continuous.
Again, I don’t have the physics training or the mathematics understanding to make much of these theories, and Becker’s article does not supply the supporting equations. Still, to me, these theories all seem to be conjectures for which the creators can write equations that balance out and don’t violate any known principles, but otherwise they are just fanciful imaginings.3
But one part of the article that did strike me intuitively was the question of how spacetime could be emergent in the first place, quoted from Eleanor Knox, a philosopher of science at King’s College London. She noted that we humans are land animals, and our direct ancestors developed on the African savannah. There we became attuned to the vast distances that we could see and the threats of predators and opportunities for prey, represented by physical beings crossing that landscape. Everywhere we looked on Earth and out into the distances beyond the sky we saw physical objects moving through space and time. No wonder then that we thought these things, the space they filled, and the time that passed while they had that location and held that form, were the basis of ultimate reality.
As I tried to absorb the article’s theories, especially after the mental dislocation of Knox’s suggestion, it occurred to me that if space and time and their relationship to gravity emerge from any underlying, ultimate principle, that reality is energy. Energy in different forms is the root cause of and the motivation for everything we see and experience.
Our chemistry and physics break down everything we can see and touch into molecules, which are made up of atoms. Atoms are divisible into complex particles called “hadrons”—the protons and neutrons in the nucleus—that are made up of various combinations of supposedly indivisible, or “elementary,” particles called “quarks.” These quarks come in six types or “flavors” in what quantum mechanics calls the “Standard Model.” Other elementary particles are “leptons,” which include the electron that orbits the atomic nucleus and various kinds of neutrino that, among other things, can distinguish a proton from a neutron. There are also elementary particles called “bosons” that carry force, such as the photon that rides a wave which, at different frequencies, is responsible for everything from radio and television signals to heat and light to x-rays and gamma rays.
From one point of view, all of these particles are real things with known qualities like their spin and quantities like their mass. For example, sometimes a photon—which has no measurable mass—acts like a solid particle in some experiments. From another point of view, every one of these particles can, when brought together with sufficient force in a particle accelerator, disappear into a cloud of pure energy that only subsequently resolves itself into new and different particles. And sometimes, in some experiments, a photon acts just like a wave with no physical, thing-like presence at all.
So what is matter, really? Under the closest scrutiny, the most thinly sliced reality, matter is made up of frozen bits of energy that temporarily have a physical identity and a locatable spatiotemporal address. But jostle it hard enough, and it evaporates into a flare of energy. Einstein understood this with his equation e=mc2, or “energy equals mass times the speed of light squared.”
You can test this for yourself. Are you a thing or a form of energy? As a thing, I am a few pounds of common chemicals knit together into complex molecules that interact through certain electromagnetic attractions, all while suspended in a hundred or two hundred pounds of water. My thingness is interesting to a biologist, perhaps, but its thingy nature doesn’t change much from the time two hours before I die, when I am alive, to two hours after the event, when I am cold and dead. On the other hand, as a process, I am very active at the one point and inert or nonexistent at the other. As a thing, my chemical makeup changes daily. My components and physical form change visibly from one year or decade to the next. But the characteristic that makes me a vital, continuous identity—the energy represented by all my assembled and interacting chemical-and-metabolic, neuronal-and-mental processes, and the mind and memories that result from them—is very real. I have a temporary physical identity and a locatable spatiotemporal address, but at heart I am a stream of energy.
Consider the Big Bang.4 From the point of view in which space and time are the ultimate reality, the event started with a compressed state of matter, with all of the atoms now composing our visible universe crowded into a single, compact mass. And that mass suddenly destabilized and dispersed into previously existing and waiting space. But from the point of view with energy as the fundamental reality, this was an outpouring of energy that eventually condensed, organized itself into localized particles, and defined space and time as a result.
Consider black holes. From one point of view, they are concentrations of mass into a space so small that their gravity overwhelms local conditions of time and space. From the other, they are concentrations of energy—for gravity is clearly a form of energy, or else why do the quantum physicists keep trying to encumber it with a so-far-undetected force particle, the graviton? The amount of energy contained in the thing we call a “black hole” annihilates both space and time and, along with them, matter itself.
Consider that kinetic energy and inertia can increase the apparent mass of any object. This is why a bump with a four-pound fist, or a four-thousand-pound automobile, is different when the object is traveling at two miles an hour from when it is traveling sixty miles an hour. The thing itself has not changed, but its energy certainly has.
In our real and observable world, distance is only meaningful in terms of the energy needed to travel from one point to the next, and time is only meaningful in terms of the energy needed to power the events, actions, or processes by which it is counted. These things appear to be separately meaningful to our brains in our perceived reality as land-based hominids having to walk across the savannah or throw a stone or spear to bring down prey for our next meal. But the underlying reality is the energy involved.
All of this raises a philosophical or existential question. What is a painting? What is any work of art, for that matter? Is the painting “really”—that is, its ultimate reality—defined by the canvas that supports the paint? Is it the pigments in their base of oil or acrylic, which reflect certain wavelengths of visible light and not others to the observer’s retina? Is it energy that applied those materials in their lines and sweeps across the canvas? Or is the painting “really” the artist’s intention that selected those particular pigments and directed the brush in applying them? Without that energy of selection and application, the painting has no underlying reality, and the canvas has no meaningful dimension. Without the sculptor’s application of hammer and chisel, the marble has no final shape. Without the potter’s intention expressed through her fingers and the pressure they exert, the clay is just a formless lump.
Energy in both its active and temporarily frozen forms defines space and time. Energy is the ultimate reality and underlying fundamental of the world we see around us. It’s not the savannah, and not the rock or spear, but the way energy shapes their relationship that makes them important in our human perception.
1. Unfortunately, the actual text of Becker’s article is behind a paywall. He is also the author of the book What Is Real?: The Unfinished Quest for the Meaning of Quantum Physics, in which he analyzes the question, first raised by some of the originators of quantum mechanics themselves, of whether their theories represent anything that exists in the real world itself or are just an imaginative system supported by their mathematics.
2. For some background on my interest in this question, see my two blogs Three Things We Don’t Know About Physics (I) from December 30, 2012, and (II) from January 6, 2013. My point there is that we simply do not understand or have a real definition of the effects we see as gravity, space, and time. I freely admit that I am not trained in physics, have an inadequate background in mathematics to understand most of the physicists’ equations, and just stand here questioning. But I also think—like Becker in the article—that we’re missing something big.
3. To understand the depths of my mathematical ignorance, see the blogs from 2010, Fun With Numbers (I) on September 19 and (II) from September 26, as well as Fun With Negative Numbers from November 3, 2013.
4. I am always cautious when citing the Big Bang. It strikes me as something we haven’t fully examined. We discovered at one point in time—when we started observing the universe with sophisticated telescopes operating at various wavelengths—that it was expanding. We could think of no reason for this expansion, or what might stop it, or how it might change over a time span longer than humanity’s brief life on Earth. And so we “ran the film backwards” to a computed point in time and space when everything we could see in the cosmos was all bound into an infinitely small, infinitely dense particle. There are aspects to the process of expansion from there—like the necessary period of “inflation,” which brings the universe to its currently observed size by having the expansion briefly exceed the speed of light—that make no sense to a rational person. But it all gives the universe a starting point, a creation story, and human beings appear to need creation stories.